Prevalence of sleep complaints: a questionnaire-based study of a Swiss working population

Background: The aim of the study was to demonstrate the variety of sleep disorders occuring in a working population in Switzerland and to estimate the prevalence of the main sleep disorders in this Swiss cohort. We also intended to demonstrate that with just a few systematic questions a straightforward diagnostic workup is possible in general practice. Methods: A questionnaire was sent to all 1473 clerks of the Berne main post office. The questions allowed a choice between "yes" or "no", or often (= +++), occasionally (= ++), rarely (= +) and never (= 0). Daytime sleepiness was assessed by the Epworth Sleepiness Scale. Results: 668 questionnaires (45%) were available for analysis. Daytime sleepiness, assessed by an Epworth score greater than or equal to 10, was found in 13% of the respondents. Short sleep (<7 h sleep) was reported in 47%, and long sleep (>9 h sleep) in 5%, of this population. Specific questions clearly suggested obstructive sleep apnoea in 6%, restless-legs syndrome in 4%, disorders of initiating and maintaining sleep in 19% and narcolepsy in 0.5% of respondents. Conclusion: Chronic sleep insufficiency and sleep complaints appear to be frequent in this relatively young Swiss working population. The questionnaire-based estimated prevalence of the main sleep disorders is comparable to previously published international data.